Chemical vaporizer for material deposition systems and associated methods

ABSTRACT

System and method for operating a material deposition system are disclosed. In one embodiment, the method can include periodically injecting a precursor into a vaporizer through an injector at the vaporizer, vaporizing the precursor in the vaporizer and supplying the vaporized precursor to a reaction chamber in fluid communication with the vaporizer, and shutting down the vaporizer and the reaction chamber after a period of time. The method can also include conducting maintenance of the injector at the vaporizer by using a vapor solvent rinse.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/830,688filed Jul. 30, 2007, now U.S. Pat. No. 7,883,745, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to material deposition systems forperforming chemical vapor deposition processes, including continuousvapor deposition and/or pulsed vapor deposition (e.g., atomic layerdeposition processes.)

BACKGROUND

In manufacturing integrated circuits, various thin films are depositedand patterned on a semiconductor substrate. One deposition process iscontinuous chemical vapor deposition (CVD). In a continuous CVD process,a gaseous precursor is delivered to a reaction chamber to contact aheated substrate, e.g., a semiconductor workpiece. The precursor thendissociates in a chemical reaction to coat the substrate with a layer ofdeposited material. Another deposition process is pulsed CVD, whichincludes delivering one or more gas precursors in pulses. Atomic layerdeposition (ALD) is one pulsed CVD process. In an ALD process, a layerof first chemical forms on a substrate surface and self limits to amonolayer. The first chemical is then purged from the system. A secondchemical is then introduced to react with the first chemical and is thenpurged from the system. This process can be repeated until a layer ofthe desired thickness is deposited onto the substrate.

In both continuous CVD and ALD processes, the precursor must bedelivered in a gaseous state. Many potentially useful precursors haverelatively high vaporization temperatures, and these precursors must beheated in a vaporizer before being delivered to the reaction chamber.However, such heating can adversely affect certain precursors. Forexample, some precursors can decompose at elevated temperatures andcontaminate and/or clog the vaporizer and/or other components of adeposition system. The deposition system typically must be shut down forclogged or contaminated lines, which can reduce product throughput andincrease manufacturing cost. Therefore, there is a need for efficientlyand cost-effectively maintain the vaporizer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a material deposition system duringnormal operation in accordance with an embodiment of the disclosure.

FIG. 2 is a schematic diagram of the material deposition system of FIG.1 during a maintenance procedure in accordance with an embodiment of thedisclosure.

FIG. 3 is a functional diagram illustrating software modules suitablefor use in the material deposition system of FIG. 1.

FIG. 4 is a flow chart illustrating a method of cleaning an injectorsuitable for use in the system of FIG. 1 and FIG. 2.

DETAILED DESCRIPTION

Specific details of several embodiments of the disclosure are describedbelow with reference to a material deposition system and methods forsupplying a gaseous precursor to the material deposition system. Severalother embodiments of the material deposition system may have differentconfigurations, components, or procedures than those described in thissection. A person of ordinary skill in the art, therefore, willaccordingly understand that the invention may have other embodimentswith additional elements, or the invention may have other embodimentswithout several of the elements shown and described below with referenceto FIGS. 1-4.

Even though embodiments of the material deposition system are discussedbelow primarily in the context of chemical vapor deposition such asatomic layer deposition, aspects of the invention may be useful in anythin film deposition or etching technique requiring a source of gaseousprecursors. Such techniques may include, for example, metal organicchemical vapor deposition, atmospheric pressure vapor deposition, lowpressure chemical vapor deposition, plasma enhanced low pressure vapordeposition, atomic layer deposition, and molecular beam epitaxy.Likewise, the following discussion focuses primarily on methods andapparatus for processing semiconductor workpieces, but in certainembodiments, the substrate may comprise silicon, gallium arsenide,glass, an insulating material such as sapphire, or any other substratematerial upon which thin films may be deposited.

FIG. 1 is a schematic diagram of a material deposition system 10 duringnormal operation in accordance with an embodiment of the disclosure. Thesystem 10 can include a reaction chamber 20, a vaporizer 30 forvaporizing a precursor 11, and a delivery line 21 connecting thevaporizer 30 to the reaction chamber 20 for supplying the vaporizedprecursor 11 to the reaction chamber 20. The precursor 11 can containtrischlorodiethylamino titanium (TCDEAT), bis-ditertbutyl-diketimidestrontium (SDBK), and/or other suitable chemical compounds. The system10 can also include a chamber inlet valve 54 in the delivery line 21 toregulate a precursor flow to the reaction chamber 20.

The reaction chamber 20 can include a heating plate 24 to support and/orheat a semiconductor workpiece 22. The heating plate 24 can maintain theworkpiece 22 at a relatively constant elevated temperature (e.g., about100°-700° C.) during a CVD process. The heating plate 24 can includeelectrical resistance, thermoelectric, and/or other types of suitableheating elements. In some embodiments, the reaction chamber 20 can alsoinclude a gas distributor 28 adjacent to the semiconductor workpiece 22.The gas distributor 28 can control uniformity and/or the flow rate ofthe precursor 11. In certain embodiments, the system 10 can also includean optional vacuum pump 26 connected to the reaction chamber 20 formaintaining the reaction chamber 20 at a reduced pressure, e.g., betweenabout 10⁻⁷ torr and about 700 torr.

The vaporizer 30 can be a glass, quartz, and/or metal vessel having acarrier gas port 36, a solvent port 34, and an outlet port 33. Thevaporizer 30 can include an injector 32 for injecting the precursor 11into the vaporizer 30. In one embodiment, the injector 32 can begenerally similar to fuel injectors used in automobiles (e.g., solenoidinjectors). The injector 32 can be programmed to allow a desired amountof precursor 11 to enter the vaporizer 30 at predetermined timeintervals. The vaporizer 30 can also include a heater 31 for supplyingenergy to vaporize the injected precursor 11. The heater 31 can be aclam-shell external heater, an external radiation heater, an internalresistive heater, or other types of internal or external heatingdevices. The vaporizer 30 can also include a heater control 35electrically coupled to the heater 31 for monitoring and/or regulatingthe operation of the heater 31.

The system 10 can also include a precursor storage 38 holding theprecursor 11, a precursor supply line 47 between the precursor storage38 and the injector 32, and a precursor supply valve 48 in the precursorsupply line 47 for regulating a precursor flow to the vaporizer 30. Theprecursor storage 38 can be a tank constructed with glass, plastic, orother suitable material compatible with the precursor 11. In someembodiments, the precursor storage 38 can be blanketed and/orpressurized with argon, nitrogen, or other suitable inert gas. In otherembodiments, the precursor storage 38 can be open to the atmosphere.

The system 10 can further include a solvent storage 40 holding a solvent12, a solvent line 41 between the solvent storage 40 and the solventport 34, and a solvent inlet valve 42 in the solvent line 41. Thesolvent 12 can be isopropanol, tetrahyrafuran, hexane, octane, othersuitable solvents, or a mixture of the foregoing compounds. Optionally,the system 10 can further include a waste storage 50 for collecting usedsolvent from the vaporizer 30, a waste line 51 between the waste storage50 and the vaporizer 30, and a dump valve 52 in the waste line 51.

In the illustrated embodiment, the system 10 also includes an optionalcarrier gas storage 44 holding a carrier gas 13, a carrier gas line 45between the carrier gas storage 44 and the carrier gas port 36, and acarrier gas valve 46 in the carrier gas line 45. The carrier gas storage44 can be a pressurized tank holding argon, nitrogen, and/or othersuitable carrier gas 13 that can facilitate the transport of thevaporized precursor 11 to the reaction chamber 20. In other embodiments,the carrier gas storage 44, the carrier gas line 45, and the carrier gasvalve 46 can be omitted.

The system 10 can further include a controller 60 in electricalcommunication (showing in phantom lines for clarity) with the injector32, the precursor supply valve 48, the carrier gas valve 46, the solventinlet valve 42, the dump valve 52, the chamber inlet valve 54, and theheater control 35. The controller 60 can include a Programmable LogicController (PLC), a Distributed Control System (DCS), a System LogicController (SLC), a personal computer, and/or other suitable logicprocessor. The controller 60 can include a computer-readable mediumcontaining instructions for controlling the operation and maintenance ofthe system 10, as described in more detail below with reference to FIG.3. In the illustrated embodiment, the controller 60 optionally includesan operator panel 62 for providing process information to an operatorand/or receiving input from the operator. In other embodiments, theoperator panel 62 can be omitted.

During processing, the controller 60 can command the heater control 35to supply power to the heater 31 to heat and/or maintain the vaporizer30 at a desired operating temperature (e.g., 80° C.). Then, thecontroller 60 can transmit an electrical signal to the precursor supplyvalve 48. In response, the precursor supply valve 48 opens to provide aflow of the precursor 11 to the injector 32. The controller 60 can thenperiodically actuate the injector 32 for a certain period of time toinject a desired amount of precursor 11 into the vaporizer 30. Theinjected precursor 11 then vaporizes in the vaporizer 30 by absorbingheat from the heater 31. The controller 60 can then open the chamberinlet valve 54 to supply the vaporized precursor 11 to the reactionchamber 20. In some embodiments, the controller 60 can also open theoptional carrier gas valve 46 to introduce the carrier gas 13 into thevaporizer 30. The carrier gas 13 then mixes with the vaporized precursor11 before the mixture is supplied to the reaction chamber 20.

After a period of processing, the injector 32 can be clogged due tovarious reasons. For example, the temperature in the vaporizer 30 cancause the precursor 11 to decompose at the injector 32.

In one embodiment, the system 10 can include at least one sensor todetermine the period of processing before the injector 32 should bemaintained. For example, the system 10 can include a flow sensor 61(e.g., a mass flow meter) in the precursor supply line 47 to measure aflow rate of the precursor during operation. If the measured flow ratedrops below a preset threshold, then the controller can automaticallystart a maintenance procedure or can issue an alarm to an operator, andthe operator can choose whether to start a maintenance procedure. Aprecursor concentration sensor (not shown) and/or other types of sensorat the vaporizer 30, in the delivery line 21, or at the reaction chamber20 can also be used to determine the period of processing. In otherembodiments, the controller 60 can start a maintenance procedure afterprocessing one, two, or any desired number of semiconductor workpiecesin the reaction chamber 20. After performing the maintenance procedure,additional semiconductor workpieces can be processed in the reactionchamber 20. Performing the maintenance procedure in between processingsemiconductor workpieces can reduce, or even prevent, the build-up ofdecomposed precursor residue in the injector 32.

FIG. 2 is a schematic diagram of the material deposition system 10 ofFIG. 1 during a maintenance procedure in accordance with an embodimentof the disclosure. To maintain the vaporizer 30, the controller 60 canfirst stop all material flows into the vaporizer 30 by closing theprecursor supply valve 48, the carrier gas valve 46, and the chamberinlet valve 54. The controller 60 can also command the heater control 35to reach a maintenance temperature. The maintenance temperature can begreater than, less than, or generally similar to the operatingtemperature of the vaporizer 30. The controller 60 can then open thesolvent inlet valve 42 to introduce a sufficient amount of solvent 12into the vaporizer 30 such that at least a portion of the solvent 12remains in the liquid phase after being introduced into the vaporizer30. As a result, the solvent 12 in the vaporizer 30 can include a vaporphase 12 a proximate to the injector 32 and a liquid phase 12 b spacedapart from the injector 32.

The controller 60 can then close all the valves and maintain the currentcondition for a certain cleaning period (e.g., five minutes). Anoperator can adjust the cleaning period based on, for example, a currentcondition (e.g., color, viscosity, etc.) of the solvent 12 in thevaporizer 30, prior cleaning results, and/or other suitable criteria. Atthe end of the cleaning period, the controller 60 can open the dumpvalve 52 to dump the solvent 12 from the vaporizer 30 to the wastestorage 50. Then the controller 60 can repeatedly introduce additionalsolvent 12 into the vaporizer 30 to clean the injector 32 as discussedabove until a desired performance in the injector 32 is restored.

The controller 60 can determine the amount of the solvent 12 introducedinto the vaporizer 30 using several techniques. For example, thecontroller 60 can calculate the required amount based on previouslygathered empirical data. The controller 60 can also monitor the liquidcontent of the solvent 12 using a level transmitter, a conductivitytransmitter, and/or other instrument at the vaporizer 30. The controller60 can further accept input from an operator who monitors the liquidcontent of the solvent 12 in the vaporizer 30 through a sight glass orthe vaporizer 30 itself.

The vaporized solvent 12 can effectively and efficiently remove theresidue from the injector 32 and vaporizer 30. The applicants havesurprisingly discovered that the vapor solvent 12 can remove residuefrom the injector 32 better than a liquid solvent. Without being boundby theory, it is believed that a solvent reflux 14 in the vaporizer 30causes such a surprising result. It is believed that the solvent 12 inthe vaporizer 30 can first evaporate from the liquid phase 12 b, and theevaporated vapor solvent can contact the injector 32 to remove anyresidue from the injector 32. After contacting the injector 32, thevapor solvent can condense and return to the liquid phase 12 b alongwith any removed residue. The evaporation-condensation process can thenbe repeated to collect more residue from the injector 32.

Several embodiments of the system 10 can be cost-effective to operatebecause the injector 32 can be efficiently cleaned. In conventionalsystems, once the injector 32 is clogged, the system 10 has to be shutdown in order to replace the injector 32 and to clean the vaporizer 30.Replacing the injector 32 can increase the production cost and thedowntime of the system 10. As a result, by efficiently cleaning theinjector 32 without removing the injector 32 from the vaporizer 30, suchshutdown, replacement, and cleaning can be avoided, and producethroughput can be increased.

The system 10 can have other configurations in addition to or in lieu ofthe configuration shown in FIG. 1 and FIG. 2. For example, the system 10can further include a precursor recirculation pump (not shown) in theprecursor supply line 47 and a precursor return line (not shown) betweenthe precursor storage 38 and the injector 32. During operation, therecirculation pump can continuously recirculate the precursor 11 betweenthe precursor storage 38 and the injector 32. Recirculating theprecursor 11 can at least reduce the exposure of the precursor 11 to thetemperature in the vaporizer 30 and dilute and/or filter, any decomposedprecursor.

FIG. 3 illustrates a functional diagram showing software modulessuitable for use in the controller 60. Each component can be a computerprogram, procedure, or process written as source code in a conventionalprogramming language, such as the C++ programming language, and can bepresented for execution by a processor 100 of the controller 60. Thevarious implementations of the source code and object and byte codes canbe stored on a computer-readable storage medium or embodied on atransmission medium in a carrier wave. The modules can include an inputmodule 102, a database module 104, a process module 106, an outputmodule 108, and optionally, a display module 110. In another embodiment,the software modules can be presented for execution by the CPU of anetwork server in a distributed computing scheme.

In operation, the input module 102 accepts an operator input from anoperator via the operator panel 62 and communicates the acceptedinformation or selections to other components for further processing.For example, the input module 102 can accept from the operator the timeinterval for actuating the injector 32, a temperature setpoint for theheater control 35, and/or other process setpoints. The input module 102can also accept from the operator selections for entering maintenancemode, starting normal processing, starting/stopping the heater 31,and/or other control selections.

The database module 104 organizes records, including operatingparameters 122, operator activities 124, and alarms 126, and facilitatesstoring and retrieving these records to and from a database 120. Anytype of database organization can be utilized, including a flat filesystem, hierarchical database, relational database, or distributeddatabase, such as provided by a database vendor such as OracleCorporation, Redwood Shores, Calif.

The process module 106 can generate control signals based on inputsignals 112, operator input received via the input module 102, and/orinternal components (e.g., an internal clock, a sequencer, timers,counters, PID control loops, etc.). For example, the process module 106can include an internal sequencer (not shown) for carrying out amaintenance procedure. The sequencer can include timers, counters, andother logic components to generate control signals corresponding toindividual stages of the maintenance procedure. The process module 106can also include comparison heuristics for generating alarms 126 thatcan be stored in the database 120.

The output module 108 can generate output signals 114 based on thecontrol signals from the process module 106. For example, the outputmodule 108 can convert the generated control signals into 4-20 mA outputsignals 114 suitable for a direct current voltage modulator, or discretesignals for actuating a solenoid valve. The processor 100 can optionallyinclude the display module 110 for displaying, printing, or downloadingthe input signals 112 and output signals 114 via devices such as theoperator panel 62 (FIG. 1). A suitable display module 110 can be a videodriver that enables the processor 100 to display the input signals 112on the operator panel 62.

FIG. 4 is a flow chart illustrating a method 150 of cleaning an injectorsuitable for use in the system 10 of FIG. 1 and FIG. 2. The method 150can include stopping all flows to a vaporizer (block 152). For example,valves to the vaporizer can be closed such that no material can enterthe vaporizer. The method can also include a solvent cleaning procedure153 for removing residue from the injector and the vaporizer. Thesolvent cleaning procedure 153 can include introducing a solvent intothe vaporizer such that at least a portion of the introduced solventremains in the liquid phase (block 154). In one embodiment, excesssolvent can be introduced to avoid completely vaporizing the introducedsolvent. In other embodiments, the liquid content of the introducedsolvent can be monitored and additional solvent can be added to avoidcomplete vaporization by using, for example, a level transmitter, asight glass, and/or other instrument operatively coupled to thevaporizer.

The solvent cleaning procedure 153 also includes allowing the introducedsolvent to reflux in the vaporizer after the solvent is introduced for aperiod of time (block 156). An operator can adjust the period forallowing the solvent to reflux based on several process parameters. Forexample, the operator can adjust the period based on a current condition(e.g., level, color, viscosity, etc.) of the solvent in the vaporizer orbased on prior cleaning results.

Without being bound by theory, it is believed that the introducedsolvent can reflux in the vaporizer because the solvent liquid is inexcess. As a result, at least a portion of the introduced solvent canremain in the liquid phase, and an equilibrium exists between the liquidand vapor phases under the current pressure condition in the vaporizer.Thus, the solvent can evaporate from the liquid phase into the vaporphase to contact the injector before condensing back into the liquidphase. It is believed that contacting the injector with the solventvapor can dissolve, combine, or otherwise remove residue from theinjector as well as the vaporizer body. In some embodiments, such refluxcan be enhanced by heating the vaporizer at a first end and cooling itat a second end spaced apart from the first end. For example, the firstend can be heated by a heater, and the injector can be cooled by acirculating precursor solution. In other embodiments, other techniquesto enhance the solvent reflux can also be used.

The solvent cleaning procedure 153 further includes purging the solventfrom the vaporizer after allowing the solvent to reflux for the periodof time (block 158). The method 150 further includes a decision block160 in which a determination is made regarding whether to repeat thesolvent cleaning procedure 153. If the answer is no, the process ends.If the answer is yes, the process reverts to block 154. In oneembodiment, the determination can be made based on a current conditionof the injector after the previous cleaning procedure 153. For example,if the injector performs satisfactorily in a test, then the process canend; otherwise, the solvent cleaning procedure 153 can be repeated. Inother embodiments, the determination can be made based on othercriteria.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. For example, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the invention is notlimited except as by the appended claims.

1. A system for depositing a material onto a semiconductor workpiece,comprising: a reaction chamber; a vaporizer having an injector; achamber inlet valve through which a vapor flows from the vaporizer tothe reaction chamber; a precursor supply valve through which a precursorflows to the injector; a solvent inlet valve through which a solventflows to the vaporizer; and a controller operably coupled to theinjector, the chamber inlet valve, the precursor supply valve, and thesolvent inlet valve, the controller having a computer-readable mediumcontaining instructions that cause the controller to perform a methodcomprising closing the chamber inlet valve and the precursor supplyvalve; and thereafter, opening the solvent inlet valve to introduce anamount of the solvent into the vaporizer, the amount of the solventbeing sufficient such that an equilibrium between a vapor phase and aliquid phase of the solvent co-exist in the vaporizer.
 2. The system ofclaim 1 wherein the method performed by the controller further comprisesdetermining the amount of the introduced solvent based on previouslygathered empirical data, and/or an input from an operator.
 3. The systemof claim 1 wherein the method performed by the controller furthercomprises monitoring a liquid content of the solvent in the vaporizer.4. The system of claim 1 wherein the method performed by the controllerfurther comprises maintaining the equilibrium in the vaporizer for aperiod of time.
 5. The system of claim 1 wherein the method performed bythe controller further comprises heating the vaporizer at a first endspaced apart from the injector and cooling the vaporizer at a second endproximate to the injector.
 6. The system of claim 1 wherein the methodperformed by the controller further comprises purging the introducedsolvent from the vaporizer and introducing additional solvent into thevaporizer.
 7. The system of claim 1 wherein the method performed by thecontroller further comprises: opening the precursor supply valve tosupply the precursor to the injector; periodically injecting theprecursor into the vaporizer through the injector; and vaporizing theprecursor in the vaporizer and opening the chamber inlet valve to supplythe vaporized precursor to the reaction chamber.
 8. The system of claim1, wherein the method performed by the controller further comprises:partially vaporizing the introduced solvent in the vaporizer into avapor phase and a liquid phase, the vapor phase being proximate to theinjector and the liquid phase being spaced apart from the injector;contacting the solvent in the vapor phase with the injector; andremoving contaminants from the injector to the solvent in the vaporphase.
 9. The system of claim 8, wherein the method performed by thecontroller further comprises maintaining the vapor phase and the liquidphase of the solvent for a period of time.
 10. The system of claim 8,wherein the method performed by the controller further comprisesexposing at least a portion of the injector to a circulating precursorflow and condensing the solvent in the vapor phase after contacting theinjector.
 11. The system of claim 8, further comprising a heater, andwherein the method performed by the controller further comprisessupplying heat via the heater to the vaporizer and continuallyvaporizing the solvent in the liquid phase with the supplied heat. 12.The system of claim 8, wherein the method performed by the controllerfurther comprises monitoring a liquid content of the introduced solventand ensuring at least a portion of the introduced solvent remains in theliquid phase.